1. Field of the Invention
The present invention concerns a mechanism which can be used, in particular, in a sonar and is designed to be submerged in a marine environment, generally at the end of a cable at depths of several hundreds of meters. The mechanism is designed to give motion of translation of one or more elements of the sonar. This motion is designed to cause one or more hinged arms to pivot between positions substantially at 90 degrees with respect to one another: an "arm down" position and an "arm stretched" position.
2. Description of the Prior Art
There are known mechanisms such as this wherein the motion of translation is given by a nut mounted in a slide and screwed on to threaded rod which forms the shaft of an electrical motor. These known mechanisms have various drawbacks: the revolving joint which is placed around the shaft, at the outlet of the motor power unit, and which is necessary for the imperviousness of the motor, is very difficult to make and greatly brakes the motor. Moreover, the mechanism is generally part of an apparatus which, after having been submerged with the arms in the stretched position, should be raised again to the surface with the arms in the down position, by means of a cable drawn by a winch. Now if a failure in the electrical supply to the motor of the mechanism or a malfunction in this motor occurs during the use of the apparatus, the raising of the apparatus is slowed down by the arms which cannot be lowered in order to be positioned flat against the wall of the body of the apparatus. The arms may even get pulled off during the raising operation.